This application claims the priority of the commonly owned copending German patent application Serial No. 100 21 614.5 filed May 4, 2000. The disclosure of such German patent application, as well as that of each US and/or foreign patent and patent application identified in the specification of the present application is incorporated herein by reference.
The invention relates to improvements in methods of and in apparatus for sharpening one or more knives which is or are mounted on a rotary knife holder. More particularly, the invention relates to improvements in methods and apparatus which can be resorted to with advantage for automatic adjustment and sharpening of orbiting knives of the type employed in the tobacco processing industry to convert a continuous body (often called cake) of compacted fragments of tobacco leaves into a flow of shreds which are assembled into a so-called filler, namely into a continuous rod-shaped body which is ready to be draped into a continuous cigarette paper web or the like.
Certain presently known apparatus which are utilized to shred compacted fragments of tobacco leaves into shapes ready to be fed into a cigarette rod making machine (e.g., a machine known as PROTOS) are distributed by the assignee of the present application); such apparatus include those which are known all over the world as KT 2 cutters (also distributed by the assignee of the present application). The apparatus and the method of the present invention can be put to use by resorting to and in KT 2 cutters.
German patent No. 29 21 665 discloses a tobacco cutter (shredder) wherein a rotary holder carries at least one adjustable knife which orbits about a fixed axis and the cutting edge of which is sharpened by a grinding tool. The knife or knives are adjustable relative to the holder in order to compensate for wear attributable to repeated severing of a mass of compacted tobacco particles as well as to removal of knife material by the grinding implement.
The patented cutter employs a step-down transmission which serves to couple the drive for the knife holder with the knife adjusting system. The arrangement is such that the rate at which the knife or knives is or are shifted relative to the holder is determined by the step-down transmission. In order to change the speed of knife feed, one must manually adjust the operative connection between the step-down transmission and the knife or knives.
An object of the instant invention is to provide a novel and improved method of automatically compensating for wear upon one or more knives which are orbited by a rotary knife holder and undergo wear as a result of (a) repeated engagement with the commodity (such as the leader of a continuous cake or flow or mass of compacted fragments of tobacco leaves) and (b) repeated or continuous removal of knife material by one or more grinding and/or other knife sharpening implements.
Another object of the invention is to provide a method which can be practiced in connection with existing cutters, such as the aforementioned KT 2 cutter.
A further object of this invention is to provide a method which ensures that the rate of material removal from and the rate of adjustment of the knife or knives are selected in dependency upon all, or upon all important or relevant, parameters which influence the wear upon the knife or knives, e.g., in a tobacco shredding machine.
An additional object of the invention is to provide a novel and improved cutter or the type wherein a rotary holder carries one or more knives which orbit about the axis of the holder and undergo wear as a result of repeated contact with the material being severed (such as compacted tobacco leaves which must be shredded prior to admission into a cigarette making machine) and as a result of repeated sharpening by one or more grinding, honing and/or other material removing instrumentalities.
Still another object of the invention is to provide the above outlined cutter with novel and improved means for rendering the removal of material from and the feeding of the knife or knives dependent upon one or more important parameters which are disregarded in presently known cutters.
A further object of the invention is to provide a novel and improved automatic control system for the parts which influence the wear-dependent adjustments of the knife or knives in a tobacco shredding machine.
Another object of the invention is to provide a novel and improved method of evaluating and utilizing signals which are indicative of variable parameters of the material to be comminuted and/or of the comminuting machine.
An additional object of the invention is to provide a tobacco shredding machine wherein the knife or knives is or are sharpened only when a sharpening is necessary or advisable and only to the extent to restore the quality of the knife or knives to a desired or optimum value.
A further object of the present invention is to provide a novel and improved tobacco shredding apparatus which can carry out all of the above-enumerated novel functions and operations even though it can employ readily available standard monitoring, driving, motion transmitting and other components.
One feature of the present invention resides in the provision of a method of sharpening at least one knife which orbits along an endless path about a predetermined axis and the sharpening of which necessitates an adjustment relative to at least one sharpening tool (such as a grinding wheel) which is adjacent the path of orbital movement of the at least one knife. The improved method comprises the steps of monitoring the magnitude of torque which is required to orbit the at least one knife about the predetermined axis at a predetermined (desired or prescribed) speed, and adjusting the at least one knife relative to the at least one sharpening tool in response to departures of the magnitude of monitored torque from a predetermined range of acceptable magnitudes (this range can embrace a single acceptable magnitude or a plurality of such magnitudes).
The method can further comprise the steps of monitoring at least one of a plurality of additional parameters (i.e., parameters other than the aforediscussed torque) which influence the sharpness of the at least one knife, comparing the at least one additional parameter with a range of acceptable additional parameters, and adjusting the at least one knife relative to the at least one sharpening tool when the monitored at least one additional parameter is outside of the range of acceptable additional parameters. This method can be resorted to for automatically sharpening at least one knife which is utilized to repeatedly sever the leader of an advancing mass of compacted tobacco particles. The additional parameters can include the cross-sectional area of the leader of the advancing mass (i.e., the quantity of tobacco per unit length of the mass), the moisture content of the mass, the storage time of tobacco particles in the mass (this might exert some influence upon the moisture content of tobacco), the nature of treatment or treatments of tobacco particles prior to severing, the quantity of tobacco in the leader of the mass (this can depend upon the degree or extent of compacting of tobacco forming the mass), the homogeneousness (or lack of homogeneousness) of the mass, the percentage of comminuted tobacco leaves in the mass (as compared with the percentage of comminuted tobacco ribs, artificial tobacco or substitute tobacco), the brand or brands of tobacco in the mass, the temperature of the mass, the percentage and/or the size and/or the composition of foreign matter in the mass, the speed of advancement of the mass, and the extent of contaminatin of the at least one knife.
The monitoring step can include continuously monitoring the magnitude of torque which is required to orbit the at least one knife.
The method can further include the step of comparing the magnitude of monitored torque with the aforementioned range of acceptable magnitudes, and the adjusting step of such method can include moving the at least one knife relative to the at least one sharpening tool when the monitored torque is outside of such range. The just mentioned range can include a plurality of tolerable magnitudes of torque, and such method can further comprise the step of terminating the moving step when the monitoring step indicates that the magnitude of monitored torque is again within the required or desired range. In other words, monitoring of the magnitude of torque can be resorted to for initiation of the adjusting step as well as for termination of adjustment of the at least one knife.
As already mentioned hereinbefore, the improved method can further comprise the steps of monitoring a plurality of additional variable parameters (i.e., parameters other than torque) each of which influences the sharpness of the at least one knife to a different extent, and generating signals which denote the extent of influence of the additional parameters upon the sharpness of the at least one knife. Such method preferably further comprises the steps of processing the signals and utilizing the processed signals to adjust the at least one knife in dependency upon the influences of additional parameters upon the sharpness of the at least one knife. The processing can involve generating a single signal which is transmitted to the means for adjusting the at least one knife by taking into consideration all of the monitored parameters including the torque. The utilized step of the just discussed embodiment of the method can include adjusting the at least one knife only when the influence of additional parameters is unanticipated and exceeds a predetermined range of parameters. For example, if a first brand of tobacco is followed by a second brand the shredding of which necessitates the application of a greater force, an increase of the required torque is to be anticipated and need not necessarily result in an adjustment of the at least one knife.
The method preferably further comprises the step of at least intermittently dressing the at least one sharpening tool.
Another feature of the present invention resides in the provision of an apparatus for comminuting a mass of compacted smokable material. The apparatus comprises means for advancing the mass toward a severing or comminuting station, a knife holder which is rotatable at the comminuting station about a predetermined axis, at least one knife which is adjustably mounted on the holder for orbital movement about the axis along an endless path to repeatedly sever the leader of the mass at the comminuting station, at least one knife sharpening tool (e.g., a grinding wheel) adjacent the path of orbital movement of the at least one knife, adjustable means for displacing the at least one knife relative to the holder and relative to the at least one sharpening tool, means for applying to the holder a variable driving torque to rotate the at least one tool at a predetermined speed, means for monitoring the magnitude of the torque being actually applied to the holder to orbit the tool at the predetermined speed, and means for adjusting the at least one knife relative to the holder and the at least one sharpening tool when the magnitude of monitored torque departs from a range of acceptable magnitudes.
At least a portion of the knife displacing means is or can be borne by the holder.
The adjusting means can comprise means for comparing the monitored torque with the range of acceptable torques, i.e., the magnitude of monitored torque with the range of acceptable magnitudes.
The apparatus can further comprise at least one additional monitoring means which is arranged to generate signals denoting at least one variable parameter, namely a parameter other than the aforediscussed torque, which influences the sharpness of the at least one knife. The adjusting means of such apparatus includes means for adjusting the at least one knife when the at least one parameter is outside a range of acceptable parameters. For example, the at least one parameter can be indicative of at least one of (a) the cross-sectional area of the mass at the severing or comminuting station, (b) the moisture content of the mass, (c) the composition of the mass, (d) the nature (such as brand) of smokable material, and (e) the temperature of the mass.
The monitoring means can include means for generating first signals which denote the monitored magnitude of torque, and the apparatus can further comprise at least one additional monitoring means which is arranged to generate second signals denoting at least one variable parameter (e.g., the moisture content or the quantity of tobacco per unit length of the mass, i.e., a parameter other than torque) which influences the sharpness of the at least one knife, and the adjusting means of such apparatus can include means for processing the first and second signals into additional signals and for initiating adjustment of the at least one knife relative to the holder and relative to the at least one sharpening tool when the additional signals are outside of a predetermined range of signals.
As already mentioned above, the torque monitoring means can include means for generating signals which denote the monitored magnitude of torque; the adjusting means of such apparatus can include means for storing a range of signals denoting acceptable magnitudes of torque, means for comparing signals which denote the magnitude of monitored signals with the range of stored signals, and means for initiating adjustment of the at least one knife relative to the holder and the at least one sharpening tool when a signal which denotes the magnitude of monitored torque is outside of the range.
The advancing means can include conveyors (such as chain conveyors) which are arranged to advance smokable material along a predetermined path ending at the severing station, and means for condensing smokable material in the mass by way of at least one of the conveyors.
The adjusting means can comprise a computer (such as a microprocessor), and the monitoring means can include a sensor which is arranged to transmit signals to the computer.
The torque applying means can comprise a variable-speed electric motor or another suitable prime mover, and the monitoring means can include a suitable torque sensor which is arranged to monitor the torque being transmitted by the prime mover to the knife holder.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved cutting or comminuting apparatus itself, however, both as to its construction and the modes of assembling and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.